Oxalate-mediated detoxification and bioaccumulation of lead and cadmium in Escherichia coli K-12 MG1655

Lead (Pb) and cadmium (Cd) remain among the most persistent and hazardous heavy-metal contaminants in industrial effluents, posing severe risks to ecosystems and human health due to their non-biodegradable nature and high toxicity. In response to the limitations of conventional chemical remediation technologies, this study evaluates the potential of Escherichia coli K-12 MG1655 to function as a microbially driven system for the detoxification, sequestration and recovery of Pb and Cd. Emphasis is placed on oxalic acid production as a mechanistic basis for metal tolerance. HPLC confirmed that E. coli K-12 MG1655 synthesizes oxalic acid under metal stress, with Pb exposure eliciting the better oxalate output, providing evidence consistent with metal–oxalate-associated detoxification during metal stress. Bioaccumulation studies using inductively coupled plasma–optical emission spectrometry revealed exceptional metal removal efficiencies, reaching 99.94% for Pb and 97.77% for Cd at 1,000 p.p.m., while Pb+Cd mixed-metal systems maintained high overall uptake (98.19%). These results demonstrate that E. coli can sequester metals across a wide concentration range with minimal inhibition from competitive ion interactions. Metal recovery from loaded biomass was evaluated through acid desorption and ohmic heating. Nitric acid (0.1 M HNO 3 ) achieved the highest recovery efficiencies (Pb, 98.5%; Cd, 91.5%), whereas ohmic heating yielded moderate (Pb, 45.38%; Cd, 45.83%) but environmentally favourable recovery without chemical additives. The integrated findings illustrate a complete microbial remediation–recovery cycle encompassing detoxification via oxalic acid, high-efficiency metal sequestration and effective downstream recovery. This integrative study establishes E. coli K-12 MG1655 as a promising candidate for closed-loop bioremediation systems linking detoxification, sequestration and recovery of heavy metals.